JPH05178656A - Alumina-based sintered body - Google Patents

Abstract

PURPOSE:To obtain a high dielectric constant and excellent characteristics by incorporating Mo and/or W into alumina as a base and maintaining a prescribed dielectric constant. CONSTITUTION:Al2O3 powder is blended with a sintering aid consisting of SiO2, CaO and MgO and oxides or salts of Mo and/or W convertible into metallic Mo and/or W after sintering so as to regulate the amt. of Mo and/or W after sintering to >=3.45wt.% or Cr2O3 as a colorant is further added if necessary. The resulting blend is mixed with an org. solvent, pulverized and mixed with a binder to obtain a slurry as starting material. This slurry is molded into a sheet shape and the molded bodies are laminated and fired at 1,500-1,600 deg.C for about 2 hr in an atmosphere of a humidified gaseous hydrogen-nitrogen mixture to produce the objective alumina-based sintered body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alumina sintered body used as an insulating substrate such as a semiconductor element housing package for housing a semiconductor integrated circuit element or a multilayer wiring board on which the semiconductor integrated circuit element is mounted.

[0002]

2. Description of the Related Art Conventionally, an alumina-based sintered body containing alumina as a main component is chemically extremely stable including heat resistance,
Since it has excellent mechanical strength and electrical insulation, it is used as an insulating substrate such as a semiconductor element housing package for housing a semiconductor integrated circuit element and a multilayer wiring board on which the semiconductor integrated circuit element is mounted (Japanese Patent Application Laid-Open No. 2004-242242) (See Japanese Patent Publication No. 54-102312).

[0003]

However, there is a problem that such an alumina-based sintered body has a small dielectric constant. That is, since the conventional alumina-based sintered body has been used by paying attention only to its electrical insulating property, it is not used as a dielectric and its dielectric constant is as small as 9.5 or less.

An object of the present invention is to provide an alumina-based sintered body having a high dielectric constant and excellent characteristics.

[0005]

As a result of studying the above problems, the present inventors have found that when the amount of molybdenum or tungsten added to alumina is increased, the dielectric constant tends to gradually increase. Based on this finding, the present invention has been completed.

That is, the alumina sintered body of the present invention contains alumina as a main component, contains at least 3.45% by weight of molybdenum and tungsten, and has a dielectric constant of 10.8 or more. Is characterized by.

Here, the total amount of molybdenum and tungsten is made to be 3.45% by weight or more, because if the amount is less than 3.45% by weight, the dielectric constant of 10.8 or more cannot be achieved. ..

In the alumina-based sintered body of the present invention, first, with respect to alumina (Al ₂ O ₃ ) powder, SiO ₂ , CaO,
A sintering aid made of MgO and metallic molybdenum (M
o) or molybdenum or tungsten oxide or salt to be tungsten (W) and, if necessary, chromium oxide (Cr ₂ O ₃ ) which is a colorant so that the content thereof after sintering is within the above range. Weighing, adding an organic solvent to this, mixing and pulverizing with a rotary mill, for example, and then adding a binder such as butyral resin to the mixed pulverized product and mixing, to prepare a raw material slurry.

Then, the obtained slurry is formed into a sheet by a doctor blade method, and a plurality of the formed bodies are laminated, and then, for example, in a humidified hydrogen-nitrogen mixed gas atmosphere within a range of 1500 to 1600 ° C. Baking is performed at a firing temperature for 2 hours to obtain an alumina-based sintered body.

Here, the reason why the firing is carried out in a humidified hydrogen-nitrogen mixed gas atmosphere is that SiO ₂ becomes SiO to evaporate unless it is humidified. In the humidified hydrogen-nitrogen mixed gas atmosphere as described above. The reason is that by firing at, it is possible to suppress the evaporation of SiO ₂ which is the main component of the auxiliary agent and promote the densification of the sintered body, which increases the dielectric constant.

Further, by adding an auxiliary agent, the densification of the alumina-based sintered body can be promoted, and thereby the dielectric constant can be improved. Further, by adding chromium oxide (Cr ₂ O ₃ ), it is possible to block light of all wavelengths which is going to pass through the sintered body by Cr, Mo and W, whereby the IC housed in the package is blocked. Can be prevented from malfunctioning.

[0012]

[Function] In the alumina sintered body of the present invention, alumina is
2. Increasing the amount of at least one of molybdenum and tungsten gradually increases the dielectric constant.
When it is added in an amount of 45% by weight or more, the dielectric constant becomes 10.8 or more, and the dielectric constant can be significantly improved as compared with the conventional alumina-based sintered body.

The present invention will be described below with reference to the following examples.

[0014]

EXAMPLES First, the purity is 99.8%, the average particle size is 1.8 μm.
Alumina (Al ₂ O ₃ ) powder and SiO ₂ , CaO,
MgO sintering aid and chromium oxide (Cr ₂ O ₃ )
And, the content after sintering of molybdenum or an oxide or salt of tungsten, which is at least one of molybdenum (Mo) and tungsten (W) after sintering, is shown in Table 1.
Was weighed so as to have the weight shown in Table 1, mixed and ground with an organic solvent and alumina balls in a rotary mill, and then a binder such as butyral resin was added to the mixed ground product and mixed to prepare a raw material slurry.

The thus-obtained slurry was formed into a sheet by the doctor blade method, and a plurality of the formed bodies were heat-pressed, and then 1 in a humidified hydrogen-nitrogen mixed gas atmosphere.
It was fired at a firing temperature in the range of 500 to 1600 ° C. for 2 hours to obtain an alumina-based sintered body of the present invention.

Thereafter, the alumina-based sintered body was made to have a diameter of 10
mm, 2 mm thick disk-shaped and polished by the laser flash method in the same manner to obtain a thermal conductivity of 40 mm in length, 3 mm x 4 mm square prism, and
Three-point bending strength was measured based on the specifications of S R 1601.

Similarly, a plate having a size of 50 mm in length and width and 2 mm in thickness is polished and subjected to volume resistivity (100 ° C., relative humidity 50%) according to JIS C 2141.
%) And the dielectric constant (room temperature, 1 MHz) were measured to derive the dielectric loss.

Furthermore, a metallized metal layer of tungsten is deposited on the surface of the alumina sintered body, and nickel plating is performed on the surface of the metallized metal layer.
A metal piece of low thermal expansion is brazed to this with a low melting point brazing material,
The metal piece was pulled with a tensile stress of 3 kg / mm ² , the presence or absence of peeling was confirmed, and the strength of metallization was evaluated. As a result, the alumina-based sintered body of the present invention did not peel.

The amounts of alumina and each colorant in the sintered body were measured by ICP emission spectroscopy.

The results are shown in Table 1.

[0021]

[Table 1]

According to Table 1, the alumina sintered body of the present invention has a thermal conductivity of 19 W / mK or more, a bending strength of 62 kg / mm ² or more,
Volume resistivity 3 × 10 ¹⁴ Ω · cm or more, dielectric constant 10.8
As described above, it has been found that the dielectric loss has an excellent characteristic of 7 × 10 ⁻⁴ or less. Further, the color tone of the alumina-based sintered body of the present invention was black, and the result of the test based on the strength evaluation of the metallization showed no peeling.

[0023]

As described above in detail, in the alumina-based sintered body of the present invention, since at least one of molybdenum and tungsten is added in an amount of 3.45% by weight or more, the dielectric constant becomes 10.8 or more. The dielectric constant can be improved significantly more than that.

Claims (1)

[Claims] 1. Alumina as a main component and 3.45% by weight of at least one of molybdenum and tungsten.
An alumina-based sintered body containing the above and having a dielectric constant of 10.8 or more.